Machinery and mechanical systems face potential failure when the ability of the machinery or systems to function normally is compromised due to worn components or an upset in normal operating conditions. If a worn component or process upset can be detected, then operator warning or immediate shutdown can safeguard the machinery from catastrophic failure. It is known that machinery vibration increases when problems such as worn bearings, cracked gears, lack of or contamination of lubrication, imbalance, looseness, and misalignment become worse. It is also known to measure such vibrations to detect problems such problems. For example, an increase in measured machinery vibration is used to detect worn components or process upsets and to trigger alarms or shutdowns. For such applications, it is known to use a vibration switch to detect a vibration increase and trigger an alarm or shut down sequence. A vibration switch can also be used to alert an operator of a decrease in vibration levels, as may be the case when a motor ceases to function.
It is known to use an electronic vibration switch to monitor a conditioned electrical signal from a built-in, or remotely located; vibration sensor. This arrangement typically uses a three-wire configuration. The switch mechanism itself is a circuit board with a mechanical relay that is typically housed in an electronics enclosure. The circuitry monitors vibration signals from the sensor and compares the signals with a pre-set threshold value. When the signal exceeds (or decreases below in some cases) the threshold, the switch activates the relay. Unfortunately, such devices are bulky, limiting the applications for which the devices can be used. For example, the devices are not usable upon smaller equipment. Further, the devices have a limited range, require a separate power source (three wire) and individual wiring to the respective programmable logic controller (PLC) or alarming device. For those devices that must be sealed, for example, for use in hazardous or wet environments, internal adjustments, for example, of the threshold value, are not possible. On the other hand, those devices that have internal adjustments may not be usable in hazardous or wet environments due to the lack of a properly sealed housing.
Thus, there is a long-felt need to provide a vibration switch that is less bulky, has a greater range, does not require a separate power source, has on-board intelligence, can be sealed, and is configured for internal adjustments.